Sidewall sampler



Oct. 10, 1961 F. v. PORTER ET AL SIDEWALL SAMPLER Filed May 6, 1957 www@ United States 'This invention relates to tools for taking samples of the formations penetrated by earth boreholes, and more panticularly to improved explosively actuated means for obtaining samples from the sidewalls of earth boreholes such as drilled for producing oil, gas, water and the like iiuids.

In general, explosively activated earth borehole formation sampling tools employ an elongated gun body which is adapted to be lowered into such fluid-filled earth borehole on a suitable conductor cable. 'Ihe gun body usually has a plurality of laterally directed gun bores in each of which is contained a propellant charge and a hollow or tubular shaped cutting projectile to be propelled by such propellant into penetrating impact with adjacent formation to be sampled. The projectiles are each usually held captive to the gun body, both before .and after tiring, by a flexible wire or cable by means of which the projectile, after firing, can be dislodged from the surrounding formation and retained in attachment to the gun body for subsequent retrieval from the borehole.

The use in connection with such an explosive actuated gun device of a conventional hollow, sample-cutting projectile open at the front end and closed at the rear end entails the disadvantage that fluid ordrilling mud present in the borehole or well interferes with the cutting and capture by the sample-cutting projectile of a suitable sample from the sidewall formation. The principal reason for this is that the sampler entraps uid within itself so that the entrance of the formation sample therein is blocked by such fluid and thus only a fraction of fthe hollow interior of the sampling projectile is available for receiving and containing such sample. Furthermore, under such conditions, the recovered sampleis more likely to be contaminated by having forced into it, under the resulting high pressure, components of the thus entrapped fluid or drilling mud.

To overcome these disadvantages, a tubular sampling projectile, open at both ends, has been employed. This structure results in the capture of an adequate sample in the bore of the sampling projectile relatively free of iluidderived contaminants but suffers the disadvantage that, `with some sampled formations, all or a large part of the solid components of the sample or a substantial portion of the iiuid contents of the sample may be lost before it reaches the top of the borehole due to the washing or leaching action of duids in the borehole during the samples upward vcourse therethrough as the apparatus is retrieved.

Another type of sampling projectile has been proposed having an open forward end and a rearward end temporarily closed by a detachable closure member. This closure member is prevented from moving forward in the sampling projectile but is capable of moving rearwardly out of the projectile. With this arrangement the forces developed by the propellant charge in the gun are initially directed against the rear surface of the closure member to drive the projectile into the sidewall formation. Following this the reacting duid pressure exerted against the front surface ofthe closure member from inside the forward portion of the projectile pushes the closure member rearwardly out of the barrel so that the fluid escapes from the rear of the projectile as. the formation sample enters the front end thereof.

It will be seen that this latter type of formation sampling projectile does not suffer the disadvantages of the first-mentioned projectile arrangement which is open at the forward end and closed at the rearward end, but does have the disadvantages of the second-mentioned sampling projectile which is open at both ends; namely, although an adequate, relatively uncontaminated sample may be initially captured in the sampling projectile, the sample or fluid contents thereof may under some conditions be subsequently washed out of the sampler and lost before it reaches the top of the borehole.

Diiiiculties also are encountered in retrieving sampling projectiles wherein the retrieving cable is connected directly to the side or closed end of the projectile in conventional manner. With such attachment the angle of pull of the cable relative to the axis of the projectile is often such that the full strength ofthe cable cannot be used and the cable breaks. The method o-f storing the cable may also be faulty so that sudden, powerful strains are placed on it when the projectile is shot out of the gun body. The use of twin cables is sometimes advantageous but may result in entanglement of the cables and failure of the apparatus to function properly.

Accordingly, it is an object of this invention to provide an explosively actuated sidewall formation sampler which is free of all of the hereinbefore described disadvantages and defects.

Another object of this invention is to provide a sidewall formation sampler which will result in capturing an increased amount of sample in the core barrel and will prevent washing or loss thereof after capture.

Another object is to provide such a sampler which will minimize the contamination of the captured sample with components of the borehole fluid.

A further object is to provide such a sampler wherein the sampling projectile retrieving cable arrangement and attachment is improved whereby breakage of the retrieving cable is reduced and improved efficiency in recovery of samplers from borehole sampling operations is thereby accomplished.

Briefly stated in general terms, the objects of this invention are attained by eXplosively actuated sidewall formation sampling apparatus having a gun body and one or more gun bores therein, each such gun bore initially containing a generally tubular shaped, formation sampling projectile, and having a suitable propellant charge for expelling such projectile, at high velocity, out of such bore into adjacent borehole Wall formations to be sampled, each such sampling projectile being provided with a longitudinal bore in which is contained a disc shaped partition or piston-like member longitudinally slideable therein, such piston-like member having longitudinal passages therethrough with one-way valve means associated therewith which permits escape of entrapped fluid from the forward portion of the lbore of the sampling projectile, rearwardly through such passages when the projectile is propelled forwardly into the sidewall formation and the formation enters the projectile bore but prevents passage of fluid in the opposite direction. ln a preferred embodiment, the piston-like member is initially positioned in the forward end portion of the bore of the sampling projectile for sliding movement therein rearwardly in the bore as the projectile -is ac celerated forwardly out of the gun bore toward and into the sidewall formation. The embodiment also includes attachment of the retrieving cable member to the beforementioned piston-like member with slack portions of connector to the beforementioned piston member within the sampling projectile so that the ends of the cable can align themselves in the connector devices to best advantage during and after propulsion of the sampling projectile toward the sidewall formation.

A more detailed description of a preferred embodiment of the invention is given hereinafter with reference to the drawing wherein:

FIG. 1 is an elevational View showing a gun type formation core sampling apparatus assembly positioned within a borehole;

FIG. 2 is a fragmentary vertical sectional view of a portion of the apparatus of FIG. l drawn to a larger scale than FIG. l, and showing a formation sampling projectile assembly positioned in a gun bore in the gun body;

FIG. 2A is a View in section taken on line A-A of FIG. 2; and

FIG. 3 is a view similar to FIG. 2 showing the formation sampling projectile after being tired from the gun bore of the gun body and lodged in a sidewall formation wtih a captured formation sample therein.

Referring rst primarily to FIG. 1, is an elongated, generally cylindrical body of a sidewall formation sampling apparatus suspended in operating position in an earth borehole 14, by means of a conductor cable 15. The gun body 1@ comprises an upper portion 10a which houses an electrically activated switching mechanism (not shown) for separately and sequentially electrically firing the propulsive charges for propelling the sampling projectiles from the gun body into the adjacent side- Wall formation of the borehole 14; an intermediate portion 10b in which is formed a plurality of gun units including laterally directed gun bores 19 into which are initially loaded sampling projectiles 11 and projectile propellant charges 24; and a lower portion 10c formed with an elongated recess 18 directly below the outer or muzzle ends of the gun bores 19 for receiving captive formation sampling projectiles suspended therein after being tired into and dislodged from the borehole wall, as illustrated at 11a.

Suitable laterally extending bow springs 13 and 16 are mounted on the upper and bottom end portions of the gun body for urging and positioning the gun body eccentrically with respect to the borehole axis such that the so-called rearward side of the gun body is held firmly against the side of the borehole wall while at the same time providing a maximum spacing along the opposite forward side of the gun body, whereby adequate spacing is provided between the forward or muzzle ends of the gun bores and the adjacent Vborehole wal-l, 4and also adequate clearance is provided between the recess 18 and the adjacent borehole wall to permit free clearance for the entrance and suspension therein of sampling projectiles after tiring and dislodgment as beforedescribed.

The cable usually contains one or more insulated electrical conductors (not shown) for electrically interconnecting current supply and control means located outside the top of the borehole with the beforementioned electrically activated switching mechanism housed within the upper portion 10a of the gun body. The igniter and wiring for tiring each propellant charge is described more fully in the co-pending application of Forrest V. Porter, Serial No. 610,278 filed September 17, 1956 and now Patent No. 2,848,195.

Except for positioning relative to one another, each gun unit comprising gun bore, sampling projectile, propellent change and other associated apparatus elements is identical, therefore only one such unit will be described, in more detail, hereinafter.

Referring now primarily to FIG. 2, each such gun unit includes a sampler projectile 11 initially loaded into a transverse aperture or gun bore 19 which extends through the intermediate portion 10b of the gun body 10. The gun bore 19 is formed with a number of stepwise variations in inside diameter, namely a rearward portion 20 of smallest inside diameter, a forward portion 22 of intermediate inside diameter and an intermediate annular channel portion 21 of largest inside diameter. This arrangement results in the formation of a fowardly-facing, annular shoulder 23 which joins the rear end of channel portion 21 with the forward end of bore portion 29.

The beforementioned sampling projectile is generally tubular in `character and is formed with va cylindrical rear body portion 25 of smallest outside diameter, corresponding to, but making a sliding t in the rearward portion 20 of the bore, and a forwardly located cylindrical portion 26 of relatively larger outside diameter corresponding to but making a sliding iit in the forward portion 22 of the bore. The front end portion of the exterior surface of the sampling projectile, forward of the portion 26, is pointed by a forwardly converging generally frusto-conical exterior surface portion 32 which intersects the forward portion of the projectile bore to form a relatively sharp annular cutting edge 32a. The exterior surfaces of cylindrical portions 25 and 26 are joined by a rearwardly facing, rearwardly converging frusto-conical, annular surface or shoulder 27 which together with the before mentioned forwardly-facing annular shoulder 23, the wall of the channel portion 21 of the bore and the adjacent, opposite exterior surface of the sampling projectile forms the initial boundary of an annular combustion chamber 24. An annular or suitably segmented cartridge or propellant charge 24a is initially positioned in the beforementioned combustion chamber 24, as shown. As hereinbefore mentioned, the arrangement and construction ofthe igniter for the propellant charge in chamber 24 is more fully described in co-pending application of Forrest V. Porter, Serial No. 610,278 led September 17, 1956, and now Patent No. 2, 848,195.

The sampling projectile is formed with an axial bore 34 extending therethrough from end to end, and of uniform inside diameter except for a relatively short constricted forward end portion 35 which serves as a forward piston retainer or stop and also which serves as a core sample retainer, as hereinafter explained. An annular, flanged retainer nut 36 having an inside diameter less than that of the bore 34 is threaded at 37 into the rear end of the sampling projectile 11. The annular shoulder 38 of the retainer nut thus formed also serves as a piston stop means as hereinafter explained.

A partition or piston assembly 33 is contained in the bore 34 of the sampling projectile 11 and is longitudinally slideable throughout the length thereof between the beforementioned shoulder 38 of the annular stop nut 36 and the constricted forward end portion 35.

The piston assembly 33 includes a piston member 39 having a dished or concave front face provided with an internal, rearwardly converging annular wall 40 forming a stabilizing skirt. A spherical socket 41 is formed centrally in the front face of the piston member 39, of a curvature to accommodate a swivel connector which includes a spherical bearing shell 42 which, in turn, is provided with an inner spherical surface to accommodate a connector ball 43. The rear face of the piston member 39 has a central, conical recess formed by forwardly converging annular walls 44, which enters the rearward portion of the socket 41. A series of axial passages 45, preferably arranged with centers on a circle positioned concentric with the center or axis of the piston member, are formed through the piston. The rear or outlet ends of the passages 45 are covered by a relatively thin, resilient ring-shaped valve member 46 normally to prevent tluid ow through the passages.

The connector ball 43 has an integral, radially extending, connector shank 48 firmly fixed, preferably by means such as by swaging, onto the forward sampler end of the cable 47. The valve member 46 is initially held in oontact with the rear face of the piston member 39 to cover the passages 45, and the piston assembly 33 is in general held together by a suitable resilient collar tightly fitted around the shank 48 of the connector, such as for example by means of a Tinnerman nut 49 which is press fitted onto the connector shank 48, as best shown in FIG. 3.

In loading the gun body 19 and preparing the sampler projectile for firing into the sidewall formation, the piston assembly 33 is initially disposed forwardly inside bore 34 of the sampling projectile 11 and the retrieving cable 47 is folded loosely in the remainder of the bore 34 behind the piston assembly, as shown in FlG. 2. The rearward gun unit end of the cable 47 is provided with another swivel connector which includes a ball 50 and an integralradial shank 49. The ball 50 is held seated in a socket 51 formed in a slotted recess 52 formed in the gun body adjacent the rearward opening of the man bore 2li by a keeper plate 53 secuned over the socket, as indicated at 54 and as more fully shown and described in the aforementioned co-pending Porter application, Serial No. 610,278 and now Patent No. 2,848,195. As shown particularly in FIG. 2A, socket 51 is the enlarged midportion of slot 160' which is formed between shoulder portions 101 `and 102 within recess 52. Slot 105 extends to the back of recess 52. Shank 49a fits in lower portion 104m of slot 100. The connector 49a, 50 is thus free to swivel within the limits of the recess 52.

After the samplers have been loaded into the bores of gun body 10 as hereinbefore described, and the gun body has been lowered to the desired position in the borehole Where a sample or samples are to be taken, thev gun units are fired, usually one at a time, into the sidewall formation. When a gun unit has been fired by igniting the powder charge 24 the sampling projectile is propelled at high velocity forward out of the bore and through the surrounding fluid in the borehole toward the adjacent sidewall formation. Due to the inertia of the piston assembly 33, it remains relatively stationary, moving forward only due to slight frictional forces. Relative to the sampling projectile however, the piston assembly is rapidly moved from the forward position shown in FIG. 2 to the rearward position shown in FIG. 3.

After striking the stop shoulder 38, the piston assembly 33 is carried forward with the remaining travel of the sampling projectile 11. The iiuid pressure resulting from continued rapid forward motion of the sampling projectile and entry of a sidewall formation sample as shown at 55 into bore 34, causes the resilient ring or valve member 46 to spring backward from the outlet ends of passages 45. Fluid is thus permitted to discharge from bore 34 ahead of the entering sample S5 through passages 45 until the sampling projectile 11 comes to rest in the formation, as shown in CFIG. 3. At this point the sample 55 usually has substantially filled the bore 34 of the sampling projectile to provide an adequate sample for core analysis. In such case, substantially all of the entrapped iluid or drilling mud has been discharged from bore 34- ahead of entering sample 55.

When the sampling projectile 11 comes to rest, the pressure acting in passages 45 is relieved and resilient valve member 46 springs back against the outlet ends of passages 45 to tightly close them against fluid entry from outside the rear end of bore 3'4. The captured sample 55 is thus protected from washing action or contamination by fluid in the borehole.

The imbedded sampling projectile 11 and captured sample 55 are dislodged and detached from the sidewall formation by pulling on cable and thereby elevating gun body 10. This action causes retrieving cable 47 to be pulled taut. The ball and socket arrangements 41, 42j, 43 and 5l?, 51 and the recess at 44 permit the cable attachments to swivel with respect to the axis of the taut cable and with respect to sampling projectile 11 and gun body 10, as shown in FIG. 3, so that the full strength of the cable can be utilized in dislodging the sampling projectile from the sidewall.

The dislodged sampling projectile containing the captured formation sample drops and swings into the recess 18 adjacent the lower portion of the gun body and Iemains suspended there on its retrieving cable 47 while the gun is retrieved from the borehole. Tightly closed valve member *45 prevents the captured sample 55 from being forced out of the core barrel by minimizing entry of fluid through passages 45 and into the rear end of bore 34. The suction developed in the rear end of bore 34, in addition to the action ofthe constriction 3S at the forward end thereof, assists in keeping the sample from dropping out of the bore by gravity in the event the sample is loosely held in the core barrel. The action of valve member 46 also prevents washing and minimizes contamination of the captured sample 5S while the gun body 10, together with the suspended used sampling projectiles and their captured samples, are elevated t0 the top of the well borehole.

In addition to the advantages of this invention apparent from the above description, the present construction provides a convenient and advantageous arrangement for storing and feeding retrieving cable 47. The cable is stored inside the sampling projectile bore and eliminates the need for other auxiliary cable storage facilities. Furthermore, the cable is fed from a loose yfold of slack cable with a minimum of sudden jerking action because of inertia of the piston assembly 33 permits it to lag somewhat behind the movement of the sampling projectile 11 after the propellant charge 24 is tired. Thus there is an acceleration of the sampling projectile end of the cable only over a relatively short distance toward the end of the outward travel of the sampling projectile.

While the invention has been herein illustrated and described in what is now considered to be a preferred embodiment, it is to be understood that the invention is not limited to the speciiic details thereof, but covers all changes, modifications and adaptations within the scope of the appended claims.

What is claimed is:

l. A sidewall sampler adapted to -be lowered into an earth borehole so as to obtain a sample of a desired formation intersected by said borehole, comprising: a gun body; a gun bore in said body; a sampling projectile in said gun bore and having an axial formation samplereceiving bore extending therethrough; propulsion means operatively associated with the said gun bore and said projectile for propelling said projectile from said gun bore into said formation; piston means initially disposed forwardly in the said sample-receiving bore of said projectile for slideable movement longitudinally therein between each end thereof, said piston means being formed with fluid-transfer passage means; valve means mounted on the said piston means to control fluid flow through said passage means for permitting discharge of fluid rearwardly therethrough from the forward portion of the said samplereceiving bore of said projectile as it enters said formation to capture a sample Vand for preventing the entry of fluid into the said sample-receiving bore in the opposite direction through said piston means after a sample has been captured therein; stop means formed adjacent each end of said sample-receiving bore to limit the movement of said piston means therein; cable means initially disposed in the said sample-receiving bore rearwardly of the piston means; and attachment means connecting one end of said cable means to the said piston means and the other end thereof to the gun body.

2. A sidewall sampler according to claim l wherein said attachment means connecting said cable means to said piston means comprises a swivel connector permitting limited freedom of angular movement between said cable means and said piston means without bending said cable means.

3. A sidewall sampler adapted to be lowered into an earth borehole so as to obtain a sample of a desired formation intersectcd by said borehole, comprising: a gun body; a sampling projectile carried by said gun body and having an axial formation sample-receiving bore extending therethrough, the front end of said bore being open; propulsion means associated with said projectile for propelling said projectile axially forwardly from said gun body into said formation; piston means slidably disposed in said sample-receiving bore, whereby said piston is movable between an initial position disposed forwardly in said sample-receiving bore and a final position disposed rearwardly in said sample-receiving bore, said piston means being formed with duid-transfer passage means therethrough; stop means on said projectile adjacent the rear of said sample-receiving bore to limit rearward axial movement of said piston therein; and valve means on said piston means to control Huid tiow through said passage means, said valve means permitting discharge of liuid rearwardly through said passage means, but preventing return iiow of uid forwardly through said passage means. 4. A sidewall sampler adapted to be lowered into an earth borehole so as to obtain -a sample of a desired formation intersected by said borehole, comprising: a gun body; a sampling projectile carried by said gun body and having an axial formation sample-receiving bore extending therethrough, the front end of said bore being open; propulsion means associated with said projectile for propelling said projectile axially forwardly from said gun body into said formation; piston means slidably disposed in said sample-receiving bore whereby said piston is movable between an initial position disposed forwardly in said sample-receiving bore and a iinal position disposed rearwardly in said sample-receiving bore, with said piston means being formed with fluid-transfer passage means therethrough; stop means on said projectile at the rear of said sample-receiving bore to limit rearward axial movement of said piston means therein; valve means on said piston means to control fluid iow through said passage means, said valve means permitting discharge of iiuid rearwardly through said passage means, but preventing return ow of uid forwardly through said passage means; and connection means secured to said gun body and to said projectile whereby said projectile is movable a limited distance away from its initial position in said gun body while remaining attached to said gun body.

5. A sidewall sampler adapted to be lowered into an earth borehole so as to obtain a sample of a desired formation intersected by said borehole, comprising: a gun body; a sampling projectile carried by said gun body and having an axial formation sample-receiving bore eX- tending therethrough, the front end of said bore being open; propulsion means associated with said projectile for propelling said projectile axially forwardly away from said gun body into said formation; piston means slidably disposed in said sample-receiving bore whereby said piston is movable between an initial position disposed forwardly in said sample-receiving bore and a final position disposed rearwardly in said sample-receiving bore, with said piston means being formed with fluid-transfer passage means therethrough; stop means on said projectile at the rear of said sample-receiving bore to limit rearward axial movement of said piston therein; valve means on said piston means to control fluid ow through said passage means, said valve means permitting discharge of fluid rearwardly through said passage means but preventing return tiow of liuid forwardly through said passage means; and cable means having one end attached to said gun body and the opposite end secured to said projectile, with a poriton of said cable means being initially disposed within said sample-receiving bore rearwardly of said piston means.

6. A sidewall sampler adapted to be lowered into an earth borehole so as to obtain a sample of a desired formation intersected by said borehole, comprising: a gun body; a sampling projectile carried by said gun body and having an axial formation sample-receiving bore extending therethrough, the front end of said bore being open; propulsion means associated with said projectile for propelling said projectile axially forwardly from said gun body into said formation; piston means slidably disposed in said sample-receiving bore whereby said piston is movable between an initial position disposed forwardly in said sample-receiving bore and a final position disposed rearwardly in said sample-receiving bore; stop means on said projectile adjacent the rear of said sample-receiving bore to limit rearward axial movement of said piston therein; and valve means to control fluid flow such that fluid entrapped in said sample-receiving bore between said piston means and an entering formation sample escapes from said bore when said piston means reaches said final position, but preventing reverse flow of iiuid into said bore between said piston means and said formation sample.

7. A sidewall sampler according to claim 6, and exible connection means secured adjacent one end thereof to said gun body and adjacent the other end thereof to an element of said projectile whereby said projectile is movable a limited distance away from its initial position in said gun body while remaining attached to said gun body.

8. A sidewall sampler in accordance with claim 7 in which said element of said projectile comprises said piston means.

References Cited in the file of this patent UNITED STATES PATENTS 2,055,506 Schlumberger Sept. 29, 1936 2,119,361 Schlumberger May 31, 1938 2,158,351 Ames et al. May 16, 1939 2,511,408 Lebourg June 13, 1950 2,718,265 Conrad Sept. 20, 1955 2,775,427 Leone Dec. 25, 1956 2,848,194 Porter Aug. 19, 1958 

